Data volume of the home page

What we check

We load the home page in a real browser at smartphone size, without cache and without clicking anything, and count what is transferred:

• Data volume: all files including transfer headers. Over 2 MB there is a note, over 4 MB a warning, over 8 MB a serious defect.
• Requests: every file is a request to a server. Over 100 there is a note, over 200 a warning.

In the report you also see how much falls on images, videos, scripts, stylesheets and fonts, the largest files of any kind (an autoplaying video counts too) and an estimate of the CO₂ emissions per visit. The estimate does not count towards the score.

Why it matters

The data volume is the simplest figure by which the speed of a website can be recognised. Every megabyte has to pass through the mobile network before the page is there. On the train, in the countryside or abroad on a throttled plan, 5 MB test the patience, and many visitors give up before they have seen the offer.

The number of requests works similarly: every request has a waiting time, even if the file is small. A hundred small files load more slowly than ten medium ones. Typical drivers are plugins that each load their own scripts and stylesheets, several font weights, icon collections and embedded services such as maps, chats and social media widgets.

Then there is electricity. Transferring, storing and displaying take energy in data centres, networks and on the devices of the visitors. A home page with 0.5 g CO₂e per visit instead of 2 g makes a noticeable difference at 10,000 visits a month. Public tenders increasingly require resource-efficient websites after the Web Sustainability Guidelines.

How to fix it

1. Images: the largest item on almost every website. Shrink, save as WebP or AVIF, lazy loading below the first screen. More on this in the article on images.
2. Videos: no background video that starts automatically on the home page. If you must, short, small, strongly compressed and only on large screens.
3. Scripts and plugins: deactivate what is not needed. Every WordPress plugin, every chat, every tracking tool loads along. Load maps and videos only on click.
4. Fonts: two weights are usually enough (regular, bold). Every further weight and every further font family costs 20 to 100 KB.
5. Compression and caching: with Brotli or Gzip and long cache times the second visit is almost free. More on this in the articles on compression and caching.

WordPress

Plugins such as "Asset CleanUp" or "Perfmatters" show which scripts and stylesheets load on which page and switch them off selectively. Caching plugins such as WP Rocket combine files.

Wix, Jimdo, Squarespace

The builders optimise images and scripts themselves. What can be controlled: fewer sections, galleries and embeds on the home page, no background video.

How to check it yourself

Open the developer tools (F12), "Network" tab, switch off the cache ("Disable cache") and reload the page. The bar at the bottom shows the number of requests and the transferred data volume. Sort by size to find the largest files. Tools such as websitecarbon.com estimate the CO₂ after the same model.